Re: BUG #15609: synchronous_commit=off insert performance regression with secondary indexes

From: "Saul, Jean Paolo" <paolo(dot)saul(at)verizonconnect(dot)com>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: Peter Geoghegan <pg(at)bowt(dot)ie>, Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk>, PostgreSQL mailing lists <pgsql-bugs(at)lists(dot)postgresql(dot)org>
Subject: Re: BUG #15609: synchronous_commit=off insert performance regression with secondary indexes
Date: 2019-02-05 00:51:03
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Thank you, yes that makes sense.
We only use partial Boolean indexes on large tables
or normal Boolean indexes on small (0-10M rows) queue tables that get
cleared down.

On Tue, 5 Feb 2019 at 12:08, Bruce Momjian <bruce(at)momjian(dot)us> wrote:

> On Fri, Feb 1, 2019 at 10:49:13AM +1300, Saul, Jean Paolo wrote:
> > Hi Bruce,
> >
> > Thank you for that info. We will likely migrate our boolean indexes (and
> > possibly all our low cardinality indexes) to hash after we move to PG11.
> Uh, there is rarely value in creating boolean indexes because, for an
> index to be useful, it should have high selectivity. What people often
> do is to create _partial_ indexes on true, false, or NULL values that
> are of high selectivity. Since there is only a single value in the
> index, I guess a hash index would be better than btree, but I am not
> sure.
> --
> Bruce Momjian <bruce(at)momjian(dot)us>
> EnterpriseDB
> + As you are, so once was I. As I am, so you will be. +
> + Ancient Roman grave inscription +


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